The distribution of black hole growth across the evolving galaxy population

了解星系如何形成和演化是天体物理学中最重要和最复杂的挑战之一。在每个星系的中心（包括我们自己的星系，银河系），都有一个巨大的黑洞，质量是太阳的一百万到十亿倍。现在人们认为这些巨大的黑洞可以决定它们所在星系的大部分结构和演化，尽管确切的方式和原因还不清楚。我的研究重点是星系和黑洞之间的这些重要联系。特别是，我研究的星系中的黑洞是迅速增长的物质福尔斯下降。在落入之前，这种物质会变热，在整个电磁波谱中发出大量辐射。黑洞以这种方式增长的星系被描述为具有活动星系核。我的目标是了解为什么一些星系有这些活跃的核，而在其他星系（如银河系）的黑洞并没有迅速增长。一些机制必须将物质驱动到星系的中心区域，并为黑洞的生长提供燃料，但我们还不确定这些机制是什么。此外，随着黑洞的成长释放出的巨大能量可能会对银河系的其他部分产生重大影响，加热或喷射气体，阻止新恒星的形成。因此，确定黑洞在星系生命周期内何时生长对于理解星系演化的物理学至关重要。我最近的工作表明，活跃的原子核（由不断增长的黑洞提供动力）可能会在几十万年的时间尺度上闪烁，这与星系的寿命相比相对较短。这种闪烁使得将黑洞增长的总体水平与星系人口的演化联系起来变得更加困难。为了取得进展，我们需要在类似演化阶段的大样本星系上测量黑洞增长率的分布。到目前为止，由于星系样本的大小有限，以及缺乏深入星系中心并测量中心黑洞当前增长率所需的灵敏X射线观测，因此很难如此详细地绘制黑洞增长的分布图。在未来几年内，这种情况将发生巨大变化。一个新的太空望远镜eROSITA将在X射线波长下绘制整个天空，我将用它来以前所未有的细节跟踪附近星系中的黑洞增长率。这些研究特别重要，因为黑洞的影响似乎在附近宇宙中最大的星系中最为严重。这些星系通常是圆形的，红色的，并且不会形成任何新的恒星--这可能都是由于中心的黑洞。此外，我们正在用最大的地面望远镜进行新的调查，测量来自大量极其微弱的遥远星系样本的光谱，从而揭示宇宙在不到现在年龄一半的时候星系的进化生命周期。我将联合收割机将这些新的微弱星系调查与最高质量的X射线数据（来自美国宇航局的钱德拉望远镜）结合起来，以跟踪宇宙时间这一重要早期时期的黑洞生长。这些研究的结合将提供一个全面的图片的物理机制，驱动黑洞的增长和黑洞对星系演化的影响，从早期宇宙到最近的宇宙时代。

Understanding how galaxies form and evolve over time is one of the most important and complicated challenges in astrophysics. At the centre of every galaxy (including our own galaxy, the Milky Way) there is thought to be a massive black hole that is a million to a billion times the mass of the Sun. It is now thought that these massive black holes could determine much of the structure and evolution of the galaxies which host them, although exactly how and why is still unclear.My research focuses on these important connections between galaxies and black holes. In particular, I study galaxies where the black hole is rapidly growing as matter falls in. Before falling in, this matter gets hot, emitting huge amounts of radiation over the entire electromagnetic spectrum. A galaxy where the black hole is growing in this way is described as having an active galactic nucleus. I aim to understand why some galaxies have these active nuclei, whereas in other galaxies (such as the Milky Way) the black hole is not rapidly growing. Some mechanisms must drive material into the central regions of a galaxy and fuel this black hole growth, but we are not yet sure what these mechanisms are. Furthermore, the huge amounts of energy released as the black hole grows could have a significant impact on the rest of the galaxy, heating up or ejecting gas and preventing the formation of new stars. Thus, determining when black hole growth occurs within the lifetimes of galaxies is vital to understand the physics of galaxy evolution. My recent work has shown that active nuclei (powered by growing black holes) may flicker on and off over timescales of a few hundred thousand years, which is relatively short compared to the lifetime of a galaxy. This flickering makes it much harder to link the overall levels of black hole growth to the evolution of the galaxy population. To make progress, we need to measure the *distribution* of black hole growth rates over large samples of galaxies in similar evolutionary phases. Mapping the distribution of black hole growth in such detail has, until now, been difficult due to the limited size of galaxy samples and the lack of sensitive X-ray observations that are needed to peer into the centres of galaxies and measure the current growth rate of the central black hole.Over the next few years, this situation will change dramatically. A new space telescope, eROSITA, will map the entire sky at X-ray wavelengths, which I will use to track black hole growth rates within nearby galaxies in unprecedented detail. These studies are particularly important, as the impact of black holes appears to be most severe in the biggest galaxies in the nearby Universe. These galaxies are generally round in shape, red in colour, and tend not to be forming any new stars - possibly all due to the black hole at the centre.In addition, new surveys are underway with our largest ground-based telescopes, measuring the spectrum of light from large samples of extremely faint, distant galaxies and thus revealing the evolutionary lifecycles of galaxies when the Universe was less than half its current age. I will combine these new faint galaxy surveys with the highest quality X-ray data (from NASA's Chandra telescope) to track black hole growth during this important early epoch of cosmic time. The combination of these studies will provide a comprehensive picture of the physical mechanisms that drive black hole growth and the impact of black holes on the evolution of galaxies, spanning from the early Universe to recent cosmic times.